Giải thích các bước giải:
a, $\frac{5}{12}$ -$\frac{3}{9}$ +$\frac{1}{18}$ =$\frac{5}{12}$ -$\frac{1}{3}$ +$\frac{1}{18}$ =$\frac{15}{36}$- $\frac{12}{36}$ +$\frac{2}{36}$ =$\frac{5}{36}$
b, $\frac{-2}{5}$ -$\frac{3}{5}$ .$\frac{4}{9}$ =$\frac{-2}{5}$ -$\frac{4}{15}$ =$\frac{-6}{15}$ -$\frac{4}{15}$ =$\frac{-10}{15}$ =$\frac{-2}{3}$
c, $\frac{2}{9}$ -$\frac{5}{-12}$ +$\frac{-3}{4}$ =$\frac{8}{36}$ +$\frac{15}{36}$ -$\frac{27}{36}$ =$\frac{-4}{36}$ = $\frac{-1}{9}$
d, $\frac{7}{12}$ -$\frac{27}{7}$ :$\frac{18}{7}$ = $\frac{7}{12}$ -$\frac{27}{7}$ .$\frac{7}{18}$ =$\frac{7}{12}$ -$\frac{3}{2}$ =$\frac{7}{12}$- $\frac{18}{12}$ =$\frac{-11}{12}$
Bài 2
a, $\frac{-5}{9}$ + ($\frac{17}{20}$ -$\frac{4}{9}$ )
= $\frac{5}{9}$ -$\frac{73}{180}$ = $\frac{27}{180}$
b, ($\frac{7}{15}$ -$\frac{11}{30}$ ).$\frac{-25}{3}$
= $\frac{1}{10}$ .$\frac{-25}{3}$
= $\frac{5}{6}$
c, ($\frac{5}{6}$ -$\frac{1}{2}$ ) .($\frac{8}{15}$ -$\frac{3}{15}$ )
= $\frac{1}{3}$ .$\frac{1}{3}$
= $\frac{1}{9}$
d, $\frac{11}{12}$ +$\frac{7}{16}$ :$\frac{-3}{4}$ -$\frac{13}{12}$
= $\frac{11}{12}$ +$\frac{7}{16}$ .$\frac{-4}{3}$ -$\frac{13}{12}$
= $\frac{11}{12}$ + ($\frac{-7}{12}$ )-$\frac{13}{12}$
= $\frac{-9}{12}$ =$\frac{-3}{4}$
cho xin hay nhất nhé
